Fiber optic cabling is used extensively in data communications. One reason for this is that optical fibers have higher data carrying capability as compared to conventional insulated copper wire conductors.
One problem associated with fiber optic cabling is the difficulty associated with repair and replacement of damaged cables. If even a single fiber is damaged, a considerable amount of data can be lost. Techniques have been developed over the years in an attempt to provide for ease of maintenance and repair. Typically these techniques have been directed to splicing damaged fibers, in which the damaged section of fiber and ferrule are cut away and replaced with a new fiber and ferrule section. U.S. Pat. No. 5,201,019 discloses one such type of fiber splice. The new section of fiber must be accurately aligned and spaced with respect to the existing section in order to prevent or minimize transmission losses. As a result, the splicing of a damaged fiber is an extremely difficult and time consuming operation.
An alternate method for repairing a cable is by replacing the entire length of damaged fiber. However, the location and routing of the fiber through the structure in which it is retained may make replacing the fiber a non-viable option. For example, in an aircraft which utilizes fiber optic cabling for transmitting data, such as the RAH-66 Comanche aircraft, the fiber optic cabling extends along numerous curved conduits and ducts. Replacement of a cable would require disconnecting both ends of the fiber and pulling the fiber out of the conduits. A new cable would then have to be inserted into and snaked through the conduits. Curves in the conduits may hamper or prevent the cable from being completely inserted. Hence, it is often difficult and sometimes impossible to route a new fiber in a preexisting conduit.
In these circumstances, the fiber optic cable is sometimes designed to have redundant or "dummy" fibers. That is, the cable includes additional fibers which are not needed but, instead, function as reserve fibers in case one or more primary fibers fail. The dummy fibers are routed through the entire system with the "active" fibers. Both the active and dummy fibers are plugged into cable connectors. The dummy fibers, however, are plugged into non-active passages of the connector. An example of this type of connector is shown in FIG. 1 wherein the active fibers are designated `A` and the dummy fibers are designated `D`. Repair of a damaged cable simply requires the substitution of the dummy fiber into the active passage originally occupied by the damaged fiber or, alternately, activating the entire dummy fiber.
The primary drawback to a fiber optic cable system with dummy fibers is that the termini of the dummy fibers, even though not conducting data, are still in constant contact with one another. Contact between the termini ends of the dummy fibers can produce wear and fiber degradation just as in active fibers, resulting in transmission losses through the fiber when the dummy fibers are activated.
A need therefore exists for a simple and inexpensive system for preventing damage to termini of the dummy fibers in a fiber optic cable before they are activated.